1. Field of the Invention
The invention relates generally to navigation equipment and more specifically to adapting global positioning system receivers with data/voice modems to standard radio communication transceivers over a single radio frequency link.
2. Description of the Prior Art
Global positioning system (GPS) receivers typically indicate only the navigational position of the receiver itself. In certain group settings where the positions of various remote or mobile stations needs to be known, such positions are commonly reported periodically by voice over a radio channel.
Many business, technical and military organizations could benefit from an automatic method of collecting the position of each individual remote station and any base station and by the distributing of such meter network positions to all. For example, public safety would benefit if police and fire dispatchers were equipped with GPS receiver base stations that could receive the current positions periodically of squad cars and fire engines. Other dispatching functions, such as parcel pick-up and delivery could also better coordinate their assets and service where the location of mobile units were readily available.
A large installed base of very high frequency (VHF) and ultra high frequency (UHF) radio transceivers exists that can be economically employed to communicate GPS position data between mobile and base units. The range of VHF/UHF communication generally extends 5-50 miles, and up to 250 miles through the use of ground repeaters with a continuous tone controlled sub-audible squelch function. Such transceivers are generally equipped with push-to-talk PTT microphone inputs and auxiliary speaker outputs. These inputs and outputs are available for users to plug in various accessories and are easy to use. It would be advantageous to users, such as police and fire fighting organizations, to be able to use their existing mobile communications equipment and systems in a networked GPS receiver configuration.